An initiative of affiliation to ICOS was begun in April 2008. The following organisations are currently affiliated to ICOS:
- American Name Society (ANS) (United States of America)
- Australian National Placenames Survey (Australia)
- Center for Adriatic onomastics and ethnolinguistics [Centar za jadranska onomastička istraživanja], University of Zadar (Croatia)
- Center of Onomastics in Baia Mare [Centrul de Onomastică] (Romania)
- Commission of Slavic Onomastics
- Department of Czech Language, Faculty of Arts, University of Ostrava (Czechia)
- Department of Onomastic, Czech Language Institute, Czech Academy of Sciences (Czechia)
- Department of Onomastics, Institute of Polish Language of the Polish Academy of Sciences (Poland)
- Deutsche Gesellschaft für Namenforschung (GfN) e.V. (Germany)
- English Place-Name Society (UK)
- Forschungsstelle für Namenkunde, Ortsnamenbuch des Kantons Bern (Switzerland)
- Greek Onomastic Society / Association Onomastique Grecque (Greece)
- International Institute of Jewish Genealogy (IIJG) (Israel)
- International Network for Personal Names Research
- Names Society of Southern Africa (South Africa)
- Onomastic Board of the Croatian Academy of Arts and Sciences (Croatia)
- Onomastic Commission of the State Administration of Land Surveying and Cadastre [Názvoslovná komise Českého úřadu zeměměřického a katastrálního] (Czechia)
- Onomastica e Letteratura, University of Pisa (Italy)
- Onomastika Elkartea (Sociedad Vasca de Onomástica / Société Basque d’Onomastique) (Spain)
- Peoples Names Research Network (PNRN) (Germany)
- Polish Onomastic Society [Polskie Towarzystwo Onomastyczne] (Poland)
- Research Centre of the Baltic Languages and Onomastics [Baltų kalbų ir vardyno tyrimų centras] (Lithuania)
- Scottish Place-Name Society [Comann Ainmean-Àite na h-Alba] (UK)
- Slovak Onomastic Commission [Slovenská onomastická komisia] (Slovakia)
- Société française d’onomastique (France)
- The Nordic cooperative committee for onomastic research (NORNA) (Denmark, Finland, the Faroe Islands, Greenland, Iceland, Norway, and Sweden)
If you wish your organisation to be affiliated to ICOS, and thereby to enter into an arrangement for exchanging information electronically, please contact the Secretary.